The history and construction of the lines that make up Thameslink are of considerable importance because they are what made the original ‘Thameslink’ network possible. It didn’t really work however as everyone saw London as the place where all their trains went to and any onward journeys were simply a case of using the sub-surface lines or bus to reach the capital’s other main line stations, special passenger trains being the only ones to use the full extent of the north-south ‘Thameslink’ lines prior to their final closure in the 1970s.
Further the idea of a through line across London wasn’t really conceived as such. The reason for the continuation of the tracks southwards through Snow Hill was in fact to afford the railway companies south of the Thames access to the newly built Smithfield markets. Unsurprisingly the through tracks to the south of London remained freight only and these sort of hung on until the early 1970s.
Had they closed a few years earlier they wouldn’t be there now for these were in the way of the Victoria Line. Fortunately, despite the light rail traffic it was decided the tunnels be rebuilt to accommodate the new tube works – and this alone has enabled the King’s Cross southern ticket hall and circulating areas to be expanded several times.
The Midland’s tunnels were far more suited for what became Thameslink. The older route via the Great Northern (Hotel Curve/York Way tunnels) was unsuited and had already been built over in part. However the new ‘Canal Tunnels’ give Thameslink a far better connection to the East Coast main line.
Construction of St. Pancras station looking south. Source: Twitter.
A hundred and fifty six years ago, this is the year 1862, the Midland Railway decides to extend its route from Bedford to London (instead of using the Great Northern’s route) and it chose to have a London terminus at very much the same location with onward rail connections too to the Metropolitan Railway. Both companies were in dispute and the Midland was determined to show who had the better railway! Thus St. Pancras, compared to the Great Northern’s King’s Cross station, was constructed on a much larger scale – yet the work was not without controversy either….
When the news came through that the Midland wanted to build its new terminus in Agar Town and Somers Town, both which were very populous parts of London, people were aghast. Even fewer could accept the idea of the scared burial grounds at St. Pancras being bulldozed by a whole new railway. Not only that the Midland were also planning on a railway underneath these burial grounds!
“The Midland Railway Company, it seems, is preceding with its desecration of this ancient and remarkable cemetery. A tunnel is being dug beneath the graves; but, what is still worse, a high construction on arches is to be made to pass over the centre of the burial-ground…” (Irish Times June 1866)
Eventually much of St. Pancras’ cemetery was moved to the new St. Pancras and Islington cemetery in Finchley. This did not stop the upheaval and the anger that followed the construction of St Pancras station as hundreds of homes were still demolished. A lot of the initial controversy revolved around the Midland’s link to the Metropolitan Railway.
“This havoc among the dead was largely the result of a decision to construct a double-track link between the Midland and the Metropolitan Railway, leaving the main line on the east side, just north of the North London Railway, at a point later known as St. Paul’s Road junction. Almost at once the line divided into a tunnel at 1 in 75, and it was the cut and cover work for this tunnel that broke into the graves. After passing diagonally under the main line, the tunnel recrossed it beneath St. Pancras, joining the widened Metropolitan Railway just west of that company’s King’s Cross station.” (London’s Termini by Alan A. Jackson, 1969)
It was much rued that the locals were having to go through another major upheaval in the short space of a just few years for yet another new railway – it had not been long since the same fate befell those whose homes and livelihoods stood in the way of King’s Cross station.
“St. Pancras, however, on the other hand, has long been the victim of railway speculation, having within its boundaries not only the termini, but the good stations of two of the largest railway systems in the world; and being about to make way for another which, from the magnitude of its works, bids fair to eclipse in extent the two railways just referred to, by an occupation of land and destruction of house property to an extent we believe to be unparalleled in the history of railway legislation.” (Observer December 1865)
Work began to clear the twin towns in October 1862. The first trains to travel across the Regent’s Canal to the new site did so by a temporary bridge perhaps sometime in 1865 or 1866. This allowed access to the main station site but more importantly at some stage in the works, the temporary tracks eventually continued right down to the New Road itself. This allowed equipment to be brought in to build the new lines and tunnels that would be required.
Whether it was the new tunnels down to the Metropolitan, the new main line station or even its goods station, hundreds of homes were demolished and many businesses displaced. As we have seen, “a great furore arose in the newspapers, and after protests in high quarters, more care was taken.” Yet I find from the newspapers there was still great unrest towards the Midland Railway even as its stations and lines became almost finished.
“Another of those instances of the astounding liberties which railway companies appear to consider they have a prescriptive right to take with the property of other people was brought to light at the meeting of the St. Pancras Vestry, on Wednesday afternoon, when the remaining tradesmen of Somers Town, who have already been half ruined by the Midland Railway Company in taking away the entire population lying between Skinner and Brewer streets and King’s Cross for their London terminus, waited upon that body to present a memorial praying to them to exercise their local power in preventing the Midland Company inflicting upon them still further encroachments and still deeper injury.” (Observer January 1868)

Illustrated London News, 15 February 1868, Public Domain, Link.
The very first passenger trains ran non-stop through Barlow and Scott’s famous gothic station a whole three months before its actual opening in October 1868. As the above engraving of St. Pancras’ station construction shows, the almost completed railway tunnels allowed progress to be made on the Midland Railway’s stupendous main line terminus.
“The branch to connect the Midland with the Metropolitan will pass by tunnel under the station, so that, of course, nothing can be done with the erection of the station until the tunnel has been constructed.” (Observer June 1865)
If the Midland Railway had not had the foresight to build a rail connection right beneath its new main line terminus at St. Pancras to link up with the new underground lines to Farringdon, Snow Hill and Blackfriars, Thameslink would have never come into being. The other alternative, via Kings Cross (York curve/Hotel curve) with extremely sharp curves and gradients were not ever really suited to modern needs. The new Canal Tunnels, opened in 2018, are the modern equivalent of the old King’s Cross – Metropolitan tunnels and do a far better job.
Like a lot of things, there were hopes the Midland’s new railway would be up and running earlier than actually happened. The company had hoped to begin its services to Moorgate Street in March 1868. At a directors meeting on 19th February 1868 it was announced this would not occur before 1st May 1868, with the main line station itself expected to follow sometime soon after.
At a special meeting on 1st July, the Board of Directors learned that their huge new London terminus with its cavernous roof would be not be open anytime soon although there was some anticipation trains could be running into part of it by August 1868. The Moorgate Street lines were about to be granted a certificate therefore the Midland announced Monday 13 July 1868 as the day its services would start between Bedford and Moorgate. Thus today, the date in question this post is being published, is the 150th anniversary of the new line from Bedford plus the tunnels through King’s Cross Metropolitan to Farringdon and Moorgate Street.
Long before the ‘Bedpan’ services began, main line services to Moorgate were quite sparse – as shown in the timetable below:

1929 timetable showing AM/PM Bedford – Moorgate services. (Author’s collection.)
As Monday 13 July 1868 was the day services started running to Moorgate Street, basically the Midland’s trains were running through the basement of St Pancras station long before its main line platforms had opened. It wasn’t a problem as passengers for the area could alight at King’s Cross Metropolitan.
The new railway line left the Midland’s line at St Paul’s Road Junction. The route did then, as it still does, descends a brick lined cutting before entering a double-track tunnel beneath the Regent’s Canal, beneath the great station itself and curving round to run beneath Euston and Pentonville Roads before joining the Metropolitan’s Widened Lines at King’s Cross (Met.)

Timetable showing just one up train late pm although there were more in the down direction (Author’s collection.)
Most of the stations north of St Pancras to Bedford too were opened on 13 July 1868. According to the LURS the Midland’s locomotives ventured as far as the Metropolitan’s station where it is said Met locomotives took over for the section to Moorgate Street (eg LURS November 1966.) Other reports say the switch took place at Kentish Town.
On Monday 1 January 1866 goods services from Blackfriars Bridge began operating via the Snow Hill tunnel to the Smithfield markets and Farringdon goods station. From Wednesday 3 January 1866 passenger services began. The Great Northern’s trains went to Ludgate Hill and the London Chatham & Dover to came up to Farringdon Street. In practice there was very little through running for passenger trains beyond these stations and those on the line to Moorgate. That in a nutshell is how the original Thameslink services were 150 years ago. It took a further 112 years before anyone really grasped the opportunities of having proper through passenger services using the Snow Hill tunnels.
A look at the Thameslink (Midland Railway) Tunnels route:
Map showing the Thameslink tunnels’ route. The two other lines leading off are the former Hotel/York Road curves.

Though St Pancras Thameslink’s entrance is in the main station itself, the platforms are beneath the roadway outside!
Midland Road is practically above the entire length of the new St. Pancras Thameslink station which opened in 2007. Where Midland Road turns slightly to the south west (just before Euston Road) is where the tunnels pass beneath the station – its shopping mall, cafes, toilets and Eurostar arrivals.

Nice pic of the exterior of St Pancras’ west side. The whole road in front actually lies on top of the Thameslink station!

The Thameslink tunnels pass on the right underneath the cafe, the footbridge and beneath the Eurostar arrivals.
The Sir John Betjeman sculpture is exactly above the centre line of the tunnels. These curve round towards the Eurostar platforms and beneath the Betjeman Arms on the other side of the station.

The Sir John Betjeman sculpture at St. Pancras will place one directly above the centre line of the Thameslink tunnels.
The International Platforms themselves were built so they did not exactly end above the top of the Thameslink tunnels hence reconstruction was undertaken within reasonable limits and it seems additional underpinning was not required. There have been some changes however. Instead of a bank of four escalators down to arrivals, just one bank of escalators from the International Platforms were built. I may be wrong however I think this was done deliberately to avoid the need for extensive underpinning. This pair of escalators are sited so they stand well away from the tunnels themselves. The one accessible lift down to arrivals is also suitably placed to avoid the tunnels.
Little known to most, the Thameslink tunnels pass beneath the famous 270 foot clock tower! Barlow and Scott collaborated on the new station so were clearly aware of the difficult engineering problems possessed by the tunnels below. When the station was built very deep foundations were built either side of the tunnels. The hotel itself gives the extra support necessary for the clock tower.

In the Farringdon direction (eg towards the photographer) the Thameslink tunnels pass under the clock tower’s structure then beneath this entrance to the underground’s ticket hall.

View roughly along the top of the tunnels from the clock tower towards the tube entrances at King’s Cross.
During the construction of the Victoria Line in the 1960s thought was given to closing the Midland’s tunnels as the Hotel & York Way tunnels to the Great Northern provided an alternative. However it was decided to rebuild the Midland’s tunnels. The original profile of these were too large and did not afford the space needed for the new combined ticket hall for the Northern/Piccadilly/Victoria Lines. The tunnels were rebuilt to a smaller size, however the profile within was kept the same. A length of about 75 yards was rebuilt. The photograph below shows the Midland’s tunnels being reconstructed.
Reconstruction of the Midland’s tunnels in the mid sixties looking in the direction of the clock tower.
If one goes down into the ticket hall, there’s no sign of the Thameslink tunnels. They however are below the floor of the ticket hall itself. In the next picture below they are straight below and curving slightly underneath the cash machines on the far wall in the direction of the clock tower.

The passageway below Kings Cross Square. This is actually a view looking west above the Thameslink tunnels alignment towards the St Pancras’ clock tower.
Although the trains themselves began operating this way on 13th July 1868, trains were coming down here much earlier than this. A picture in one of my books has this great scene depicting a contractor’s locomotive in early 1867 on temporary track that led towards King’s Cross Metropolitan station. As the picture clearly shows, the entire line was evidently built by cut and cover.
January 1867 scene showing the early stages of construction for St Pancras and its railway tunnels (see below for comparison.)
From research/analysis the next picture shows what I believe is the same exact scene 151 years later. The giveaway are the gasholders (at right) which were on the west side of King’s Cross station and the terrace houses in Judd Place (on the far left) alongside Euston Road, and this is the point where the Thameslink tracks presently straighten out briefly, as they do too in the 1867 picture. St Pancras new church can also be seen in the original however its not possible to see it from the same angle today.

The 1867 construction scene site, taken from approximately the same elevation as the original.
There’s always been some effort to keep consequent building above the Thameslink tunnels to a minimum (the Met tunnels don’t have that problem as they are directly under the road itself.) That’s why there’s always been these temporary buildings above. As some will remember, the temporary King’s Cross ticket halls stood here for decades. There was a proper building at one time as the picture below shows.
However its built at an angle clearly to avoid being right on top of the Midland’s (Thameslink) tunnels themselves. The square bit in the roof of the building is actually part of the air shaft for the Northern Line, this was once a lift shaft down to the platforms. This structure has always had to be accommodated in whatever arrangement is built here. Its presently the round building in front of the ticket hall entrance as the next picture shows.
King’s Cross station with the old frontage brick building, suitably aligned to avoid the Midland’s tunnels. Source: BBC.

The alignment of the Thameslink tunnels lies straight ahead towards Pentonville Road. The round building on the left accommodates the air shaft leading down to the tube platforms.

Past the ticket hall entrance and round building, we are still on top of the Thameslink tunnels! These don’t quite go under the road itself until the junction with York Way.
The Thameslink tunnels finally turn to go under Pentonville Road for a short distance. It is about at this point the old Hotel Curve led off en route to the old King’s Cross suburban station. There are a lot of tunnels at this point, including an old one that went the opposite way to enable trains to head west along the Metropolitan. This tunnel wasn’t in use very long. There is one other tunnel and that belongs to the Fleet sewer. This crosses both the Midland/Thameslink and the Metropolitan’s tunnels.

In Pentonville Road about where the Five Guys cafe is roughly, the Thameslink tunnels begin to go underneath the buildings on the ‘lighthouse’ island. It is at this very point all the tunnels finally come together and enter what was the old King’s Cross Midland station (in the years to 2007 part of this was the old Thameslink station.) The former York Way tunnel from King’s Cross station also joins at this point.

‘Five Guys’ where all the tunnels come together for the final bit into the old King’s Cross station.
Directly opposite the Five Guys is an entrance into what’s called Regent’s Place. Just down here one can see the old railway tunnel leading from the Great Northern/East Coast main line to the Metropolitan.

The old railway tunnel from the Great Northern is still visible in part. At the far end of the passageway in the distance is Pentonville Road and the same Five Guys building!
From this point in Pentonville Road the Midland’s and the Great Northern’s tracks merged onto what are known even these days as the ‘widened lines.’ These tracks, now part of Thameslink of course, run along the Circle/Hammersmith/Met tracks as far as Farringdon (and of course Moorgate until 2009.)